The present invention relates to structural components of electric vacuum devices and, more specifically, to a grid-like electrode for high-power generator devices.
The present invention can be useful as a grid-like electrode any electric vacuum device such as a grid, cathode or heater; in the case of making a cathode according to the present invention, the grid-like electrode is coated with an active emissive layer.
The present invention can be used in the chemical engineering and other industries requiring high-temperature, corrosion-resistant and other electrodes in the equipment produced.
The modern development of the art of high-power generator devices is based on the principle of increasing the output power of instruments and providing higher specific loads on the main operating members of the instruments, particularly on grids.
In well-known structures of grid-like electrodes made with the use of refractory materials such as tungsten, molybdenum and the like, in combination with various coatings, the opportunities for increasing specific loads have been substantially exhausted.
The increasing power of generator devices results in elevation of working temperatures of grids, thus causing lowered antiemission properties, recrystallization of the metal, reduced shape-stability and, consequently, high levels of thermal currents, lowered electrical and mechanical strength of the electronic instrument and breakdown thereof.
With a further increase in power, widening of the range of frequences, improvement of power characteristics and service life of instruments can be ensured only through the manufacture of grid-like electrodes from novel structural materials capable of dissipating high powers, possessing high heat-resistance and stability in operation.
Known in the art are grid-like electrodes made of pyrolytic graphite and shaped as a hollow cylinder with perforations in the form of a grid (cf. U.S. Pat. No. 3,307,063).
Pyrolytic graphite is produced by deposition thereof from a thermally decomposable gas phase.
Having fixed the process parameters (pressure and temperature), it is possible to ensure a high preferable crystalline orientation in the deposited carbon. Properties of the thus-produced layer are close to those of a graphite single crystal.
The process for the manufacture of the prior art grid-like electrode comprises shaping of a hollow cylinder in the manner specified hereinabove, removal of the superficial layer of the material to ensure the required wall thickness by, e.g. grinding, milling or ultrasonic treatment, making cells and partitions by way of abrasion, electronic-beam, electro-erosion or laser cutting.
However, this grid-like electrode and the process for making same fail to provide a satisfactory electrical strength and, besides, demand an expensive and laborious procedure of manufacture.
Furthermore, the need in a grid-like electrode featuring small dimensions of partitions and cells with a considerable length of the electrode faces difficulties associated with the provision of a high mechanical strength and rigidity of the structure.
In the maufacture of a grid-like structure by means of cutting, the cut surface can undergo exfoliation and peeling due to the laminated structure thereof, thus causing reduction in the mechanical and electrical strength of the devices. Furthermore, from pyrolytic graphite it is impossible to make a sophisticated shape of the electrode with small curvature radii, thus necessitating higher dimensions of the grid and the device on the whole.
Known in the art is a grid-like electrode for generator tubes, wherein at least a portion of the electrode directly forming the grid is manufactured from a glassy carbon. The electrode is manufactured by laser cutting the grid-like structure from a blank made of glass-carbon (cf. U.S. Pat. No. 4,137,477).
A disadvantage of this electrode structure and the process for making same resides in a low mechanical strength of the final article. It is very difficult to obtain strict dimensions of grids due to strinkage of the material during the process of manufacture. Another essential disadvantage of the prior art electrode is a high hardness of the glassy carbon close to that of corundum or diamond which substantially hinders its machining by a conventional method.
Known in the art are grid-like electrodes made of carbon fibrous threads coated by pyrolytic graphite which are soldered by means of a solder at the points of their intersection with each other and with supporting members (cf. U.S. Pat. No. 3,971,964).
The process for the manufacture of this electrode comprises coating of pieces of carbon fibrous threads with pyrographite; the resulting rigid rods are secured to the supporting members and fixed to each other at the points of intersection by soldering with a solder to form a grid-like structure.
The above-described grid-like electrodes do not provide a sufficiently high dissipation power, permissible working temperature, electrical strength and stability of characteristics.
These disadvantages stem from the necessity of using solders limiting the permissible working grid temperature, as well as the difficulty of manufacture of the required size accuracy. Furthermore, the prior art process is labour-consuming due to difficulties of shaping of the grid-like structure from rods having a high ridigity. Moreover, the prior art process necessitates high temperatures, increased power consumption and sophisticated process equipment.
The present invention is directed to the provision of such a grid-like electrode, as well as a process for producing this electrode which would have such a material and structure that would enable a higher dissipation power and elevated permissible working temperature of the electrode.
It is therefore an object of the present invention to increase the dissipation power of a grid-like electrode.
It is another object of the present invention to increase the permissible working temperature of a grid-like electrode.
It is still another object of the present invention to improve the mechanical strength of a grid-like electrode.
It is a further object of the present invention to increase the radiation factor of a grid-like electrode.
It is also an object of the present invention to increase electric strength and shape-stability of a grid-like electrode.
Still another object of the present invention is to provide a simple and relatively inexpensive process for the manufacture of a grid-like electrode which would make it possible to reduce the duration of its manufacture, lower labour and power-consumption for its manufacture and enable automation of the procedure of making of the grid-like-electrode.